Current Organic Chemistry - Volume 16, Issue 2, 2012

This update reviews the major developments on rotaxane-based shuttles during the period of August 2008 to October 2010 and is organized similarly to the previous review [1]. The progress in the field of chemical controlled shuttles can be summarized as a significant increase of the shuttling rates, second-generation pH-switchable Pd(II)-complexed rotaxanes, and new synthetic approaches, especially those based on Diels-Alder cycloadditions. The new synthetic routes allow ready access to rotaxanes that feature the template site fully incorporated into the interlocked product. This template site is unusual for active-template reactions and produces shuttles that exhibit entropy-driven translational isomerism with remarkably improved positional discrimination as was shown by the incorporation of a hydrogen-bonding TEG-station into an imine-bridged rotaxane. With respect to photochemically powered molecular switches, the most important result originated from the synthesis of a degenerate, donor-acceptor, light-gated, STOP-GO molecular shuttle. For electrochemically controllable bistable rotaxanes, the first example of a molecular shuttle with three different stations, which dramatically increase the shuttling process rate, has been reported. Finally, the last study in this review involves redox-driven switching and electrochromic responses of LC films containing a bistable [2]rotaxane. The presence of a polymer electrolyte provides new prospects for the further development of rotaxane-based molecular materials by exploiting the dynamic, anisotropic, and coherent properties of liquid crystals.

This review reports on the synthesis of 7-deazapurine (pyrrolo[2,3-d]pyrimidine) 2'-deoxyribonucleosides, including β-D- and β-L-enantiomers, fluoro derivatives, and 2',3'-dideoxyribonucleosides. It covers the various aspects of convergent nucleoside synthesis. Stereochemically defined α-D and α-L 2'-deoxyribonucleosides as well as sugar derivatives were prepared by nucleobase anion glycosylation. This glycosylation reaction is regioselective for the pyrrole nitrogen and stereoselective for β-nucleoside formation. Common glycosylation protocols lead to 7-deazapurine 2'-deoxyribonucleosides with unusual glycosylation sites. 7-Deazapurine 2',3'- dideoxyribonucleosides were also obtained from 2'-deoxy- or 3'-deoxyribonucleosides by Barton-McCombie deoxygenation, by elimination of sugar hydroxyl groups or by anion glycosylation. Another aspect of the review is the functionalization of pyrrolo[2,3-d]pyrimidine nucleosides. A broad range of reporter groups were introduced by the Sonogashira cross coupling or the copper(I)-catalyzed Huisgen- Meldal-Sharpless “click” reaction. The application of 7-deazapurine nucleosides as antiviral or anticancer agents, and the use of 7- deazapurine nucleoside triphosphates in the Sanger dideoxy DNA-sequencing are also reported.

Carbenoids are transient species whose reactivity resembles that of free carbenes. They can be generated by several procedures, for instance, by the interaction of diazo compounds with transition metals, such as copper, ruthenium and rhodium complexes. They are able to react with various unreactive substrates, and their use has become very popular among synthetic organic chemists. The carbenoid transfer reactions are a powerful set of synthetic tools that have attracted attention due to their versatility in constructing several types of bonds and, thus, are used to create a complex skeleton framework. Several catalysts have been designed and employed to promote the decomposition of diazo compounds, making these reactions very useful in organic synthesis. This review intends to illustrate the research efforts that occurred in this field during the last four years, covering novel, biologically important compounds and methodologies involving carbenoid and non-carbenoid reactions from diazo compounds.

This review is focused on current state of materials design and syntheses of organic semiconductors for thin-film field effect transistors (FETs). Recently, high performance p- or n-type organic FETs with high charge carrier mobility, high ON-OFF current ratios and high stability have been achieved due to the improvement of materials synthesis. Intrinsic electronic properties, solid-state packing, stability, and the capability of easy processing are the main issues of molecular design of these semiconductors. Various polycyclic aromatic compounds such as oligoarenes, oligoacenes, tetrathiafulvalenes and disc-like polycyclic aromatic hydrocarbons are qualified as good candidates for FETs after accurate chemical tailoring. We will give an overview of most recent progress in the material synthesis and the consequential device properties.

Many effective strategies have been developed in order to inhibit the hydrodehalogenation in the selective hydrogenation of halonitrobenzene to haloaniline. However, hydrogenolysis of the carbon-halogen bond of the produced haloaniline as a defect of the hydrogenation process could not be avoided completely over usual metal catalysts, especially at complete conversion of the substrates. In the past few years, we reported that over platinum/iron-oxide nanocomposite catalysts, the hydrodehalogenation of haloanilines was completely suppressed even at complete conversion of halonitrobenzene. Investigation by FTIR-CO probe and XPS revealed the electron transfer from Pt nanoparticles to oxygen vacancies in the activated Pt/γ-Fe2O3 catalysts, which may play an important role in completely suppressing the hydrodehalogenation of haloanilines in the hydrogenation reactions. In this review, we deal with the great efforts and remarkable contributions of different authors during the long exploration for the solutions of this hard obstacle. Stress is placed on supported metal catalysts and polymer-protected metal nanoclusters or colloid catalysts.